How Exercise Reduces Risk of Alzheimer’s Disease
By Tanya Thakur, MBBS
Alzheimer’s disease (AD) is one of the most devastating illnesses among older adults. The disease not only degrades memories but also affects one’s independence and takes a toll on family members.
AD is a progressive neurodegenerative disorder caused by the accumulation of abnormal misfolded protein deposits in the brain, including beta-amyloid plaques, tau tangles, and Hirano bodies. These deposits disrupt normal neuronal function, leading to the gradual loss of memory, cognitive skills, and, eventually, the ability to carry out daily activities.
AD is the most common cause of dementia, accounting for approximately 60 to 80 percent of cases. Presently, an estimated 6.7 million individuals in the U.S. have AD. In 2019, Alzheimer’s was ranked as the sixth leading cause of mortality among individuals aged 65 and above. Notably, between 2000 and 2019, while fatalities from stroke, heart disease, and HIV declined, deaths related to Alzheimer’s increased by more than 140 percent.
Even though scientists are working toward curing AD, we can take preventative measures by incorporating healthy habits, such as regular exercise, into our routine.
“It is a common misconception that we have minimal control over our risk of developing Alzheimer’s disease. However, nearly half of the Alzheimer’s cases could have been prevented or delayed by modifiable factors, including lifestyle changes,” says Sarita Khemani, MD, Clinical Associate professor of Medicine and Neurosurgery Hospitalist at Stanford University. “Therefore, we should do everything in our power to incorporate healthy lifestyle habits as early as possible.”
The Link Between Exercise and Alzheimer’s Disease
There are many things we can do to reduce our risk of developing dementia. Several research studies have concluded that physical activity is one of the best ways to reduce risk significantly. For example, after analyzing 16 studies on exercise and dementia, the Alzheimer’s Society found that regular exercise reduces the risk of developing dementia by 28 percent and, specifically, AD by 45 percent.
The connection between the brain and aerobic exercise is likely due to neuroplasticity, which is the brain’s ability to adapt and form new neural connections or strengthen the existing ones. During aerobic exercise, our brain expresses cAMP response element binding (CREB) proteins that influence the transcription of synaptic genes, including those encoding for brain-derived neurotrophic factor (BDNF). BDNF supports neurogenesis (the formation of new neuron cells), neuroprotection, and angiogenesis (the formation of new blood vessels). BDNF also increases the volume of gray matter and the hippocampus (the site of memory in the brain).
Physical activity also serves as a potent modulator of other health risk factors, including hypertension, hypercholesterolemia, and insulin resistance, all of which increase the risk of developing dementia. Vascular damage caused by atherosclerosis can accelerate the cognitive decline associated with AD due to reduced blood and oxygen flow to the brain, leading to hypoxia of neural cells.
“Brain changes associated with Alzheimer’s begin approximately 20 years before symptoms appear,” says Dr. Khemani. “Exercise stands out as one of the most effective strategies for prevention, offering a low-cost, non-pharmacological, and low-risk option accessible to everyone.”
The Best Exercises to Prevent Alzheimer’s
While aerobic exercise increases BDNF levels, resistance exercises, such as lifting weights, are thought to have a greater influence on insulin-like growth factor-1 (IGF-1) levels. IGF-1 is a hormone that manages the effects of growth hormone in the body and is essential for promoting cognitive abilities.
Because aerobic and resistance exercises elicit different neurophysiological changes, studies have indicated that combining both modalities can enhance exercise-induced neuroplasticity to a greater extent than either modality alone.
For example, one study compared the effects of combined aerobic and strength training, aerobic exercise alone, and no exercise on cognitive function among dementia patients. After nine weeks, the combined exercise regimen yielded the most pronounced results across cognitive domains. Also, the observed gains in both motor and cognitive areas regressed towards baseline levels more than two months post-intervention, meaning it is essential to exercise regularly to sustain its neurological benefits.
Regarding the type of aerobic exercise most effective for AD prevention, Dr. Khemani recommends incorporating sprint intervals into our workouts. “We encourage our patients to engage in moderate-intensity exercises incorporating some high-intensity interval training, if possible, as these activities have been shown to be more impactful for Alzheimer’s prevention than light exercise alone,” she says.
